Pots, clay vs plastic for Phalaenopsis

[deharti]

I live in Boise, Idaho. I am having trouble keeping the right moisture level for my Phalaenopsis. They are in house so the air is dry. They are currently in a coconut husk, sphagnum moss medium in an 8 inch plastic orchid pot.
The roots in the medium are rotting. Should I change pots, medium or both? We have low humidity here in the high desert country but it seems that a once a week watering is too much with the moss?

They are ready to be re-potted.